Ink jet printing has become recognized as a prominent contender in the digitally controlled, electronic printing arena because, e.g., of its non-impact, low-noise characteristics, its use of plain paper and its avoidance of toner transfer and fixing. Ink jet printing mechanisms can be categorized by technology as either drop on demand ink jet (DOD) or continuous ink jet (CIJ).
The first technology, “drop-on-demand” (DOD) ink jet printing, provides ink drops that impact upon a recording surface using a pressurization actuator, for example, a thermal, piezoelectric, or electrostatic actuator. One commonly practiced drop-on-demand technology uses thermal actuation to eject ink drops from a nozzle. A heater, located at or near the nozzle, heats the ink sufficiently to boil, forming a vapor bubble that creates enough internal pressure to eject an ink drop. This form of inkjet is commonly termed “thermal ink jet (TIJ).”
The second technology commonly referred to as “continuous” ink jet (CIJ) printing, uses a pressurized ink source to produce a continuous liquid jet stream of ink by forcing ink, under pressure, through a nozzle. The stream of ink is perturbed using a drop forming mechanism such that the liquid jet breaks up into drops of ink in a predictable manner. One continuous printing technology uses thermal stimulation of the liquid jet to form drops that eventually become print drops and non-print drops. Printing occurs by selectively deflecting one of the print drops and the non-print drops and catching the non-print drops. Various approaches for selectively deflecting drops have been developed including electrostatic deflection, air deflection, and thermal deflection.
Drop placement accuracy of print drops is critical in order to maintain image quality. Liquid drop build up on a drop contact face of a catcher, for example, can adversely affect drop placement accuracy. When this occurs, print drops can collide with liquid that accumulates on the drop contact face of the catcher. Additionally, a catcher, for example, a “knife-edge” catcher, that uses an edge to collect non-print drops typically needs that edge to be straight to within a few microns from one end to the other. A catcher lacking the appropriate amount of edge straightness is susceptible to liquid drop build which can lead to reduced image quality.
During assembly, the catcher has to be carefully aligned relative to a nozzle array of a continuous printhead since the angular separation between print drops and non-print drops is, typically, only a few degrees. Conventional alignment processes are typically laborious procedures and increase the cost of the printhead. When the printhead includes multiple nozzle arrays, each catcher typically needs to be aligned to its corresponding nozzle plate individually and one at a time adding cost and time to the printhead fabrication process.
Since a catcher is typically attached to a printhead frame using screws or adhesive, alignment of the catcher relative to the nozzle array can be compromised when the assembled printhead is subjected to shock, for example, during shipment or during the adhesive curing process. Additionally, a catcher is typically made from materials that are different from materials used to make the nozzle plate and therefore have different thermal coefficients of expansion. As such, alignment issues often arise when the ambient temperature changes. The problems associated with alignment and assembly are exacerbated as the length of the printhead is increased from an inch or less to page wide which could be tens of inches long.
Accordingly, there is an ongoing need to provide an improved liquid catcher for use in printheads and printing systems.